Three-way solenoid valves have long been used for controlling fluid flow in a variety of air and hydraulic systems, particularly fuel systems. Such three-way solenoid valves often control the passage of fluid under high pressure from a source to a load device and selectively interrupt the flow of pressurized fluid while simultaneously connecting the load device to a substantially unpressurized drain. Typically, a three-way valve includes a valve housing having first, second and third valve passages interconnected by an internal valve chamber containing two valve seats and a valve element movable to control fluid flow among the three valve passages by moving between
(1) a first position in which the movable valve member engages a first one of the valve seats to isolate a first one of the valve passages from the internal chamber while allowing fluid communication between the second and third valve passages through the second valve seat and internal chamber, and
(2) a second position in which the movable valve member engages the second valve seat to isolate a second one of the valve passages while allowing fluid communication between the first and third valve passages through the first valve seat and internal chamber.
Recent and upcoming legislation resulting from a concern to improve fuel economy and reduce emissions continues to place strict emissions standards on engine manufacturers. In order for new engines to meet these standards, it is necessary to produce fuel injection systems capable of achieving higher injection pressures while maintaining accurate and reliable control of the metering and timing functions. Three-way valves have been particularly useful in achieving new levels of operation by effectively controlling the flow of fuel in high pressure fuel systems, such as disclosed in PCT patent publication WO 94/27041, entitled Compact High Performance Fuel System With Accumulator. A "pin-within-a-sleeve" type three-way solenoid operated valve, such as disclosed in U.S. Pat. No. 5,396,926 issued to Pataki et al., is especially effective in handling very high fuel pressures while providing extremely fast response time. This pin-within-a-sleeve type three-way valve includes a hollow movable valve member having an armature connected to one end thereof for direct operation by a solenoid actuator assembly. A three-way valve also includes a floating inner pin telescopingly received within the hollow movable valve member. In an advanced position, the hollow movable valve member is biased into engagement with a first valve seat formed in the surrounding valve housing. In a solenoid retracted position, the movable valve member is biased against the floating inner pin to open the first valve seat and close a second valve seat located within the hollow movable valve member and positioned to be engaged by one end of the floating inner pin. This particular pin-within-a-sleeve design has been found to be especially advantageous in controlling relatively high pressure fuel flow due to its pressure balanced design. Moreover, the components of this particular valve are packaged to form a more compact assembly.
Although the pin-within-a-sleeve three-way valve disclosed in Pataki et al. functions to effectively control the timing and quantity of fuel injection, valve designers continually strive to increase pressure capability and minimize the response time, transition flow losses, leakage flow and complexity of valve assemblies, including the Pataki et al. valve.
Consequently, there exists a need for a three-way fuel injection control valve capable of effectively increasing the pressure capability and reducing valve response time, transition flow loss and leakage flow.